We were encountered few issue after the July month Microsoft patch KB4338814\KB4338815. After applying the patch users have reported about the DHCP issue and SQL fail-over cluster issue.On few servers we were not able to open the DHCP \ MS Fail-over console also and it has been fixed once we un-installed the above mentioned patches.

If you are getting “access denied,” “class not registered,” or “internal failure occurred for unknown reasons” errors then it is because of the problematic .NET July security patches and below link will help to fix the same.